Self-opening plastic closure

ABSTRACT

Self-opening plastic closures having a pouring spout including a flange, a cutting member that is moveable in the spout and a screw cap for actuating the cutting member. In this invention, the cutting member carries out a translatory cutting motion by the rotational movement of the screw cap. In order to open the sealed packaging, to which the plastic closure is attached, different torques are brought to bear. According to this invention, first means and second means engage with one another successively to produce different advance paths for each revolution of the screw cap.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a self-opening plastic closure including apour-out spout with a flange for connection to a single-layer ormulti-layer packaging foil of a closed packaging, with a cylindricalcutting element movably guided within the pour-out spout, and with ascrew cap with a lateral wall having an inner thread and with a coversurface, wherein the screw cap is screw-connected to the pour-out spoutwith an outer thread, and the screw cap and the cutting element includeelements which convert the screw movement of the screw cap into a purelytranslatory relative movement of the cutting element to the pour-outspout.

2. Discussion of Related Art

Self-opening plastic closures are to be understood as closures which arewelded or bonded onto a completely closed receptacle of a single-layeror multi-layer packaging foil, and include a cutting element which whenscrewing open the screw cap for the first time, cuts open the packagingfoil and holds it in the opened condition. The re-closure ability of theclosure from then on is only effected by the screw cap.

Plastic closures of this type have been widespread on the market forpractically 20 years. Two different types have already been disclosed inone of the earliest application of a closure of this type. Inparticular, such self-opening plastic closures are either provided witha rotating cutting element or with a cutting element which executes apurely translatory movement, such as known from European PatentReference EP 0328652. The cutting element is guided axially in thepour-out spout, and on an upper edge includes a ramp-like advancedevice, which with a corresponding ramp-like end-face of an annular wallsegment presses this cutting element downwards when screwing off thecap. Accordingly, the cutting element includes a multitude ofperforating teeth which are distributed over the entire periphery, withthe exception of a short section without teeth, in order to avoid thepackaging foil being completely separated from the packaging and fallinginto the receptacle. One problem with such a solution is thus the forceto be mustered. The complete force to be applied must practically bemustered with only a quarter revolution of the screw cap. These closurescould not assert themselves on the market due to the high forces whichare necessary in order to open such a closure.

An earlier version of a self-opening plastic closure with a rotatingcutting element is known from PCT Publication WO 95/05996. With thisclosure, the pour-out spout includes an inner thread, in which thecutting element with an outer thread is mounted. The screw cap which hasa peripheral lateral wall and a cover surface, on the inner side of thecover surface has at least one catch which on screwing open cooperateswith a catch on the inner wall of the cutting element and then screwsthe cutting element downwards while the screw cap is screwed awayupwards. Here too, the cutting element includes a multitude ofperforating teeth which also all act simultaneously upon the packagingfoil. Here too, a very large force is required, in order to carry outthe opening, wherein here however one requires less force due to asignificantly longer screw path. Despite this, it could initially behardly realized for such a packaging foil to be opened, in particular ifthe so-called composite foils consist of a plurality of layers ofplastic, cardboard, aluminium and once again plastic. Accordingly, it isenvisioned to provide the packaging with a punched opening and bondingor welding this opening with a thin foil which can be easily cut open.Such solutions of course are expensive and complicated, and have thegreat disadvantage that the closures must be welded on in a very precisemanner with regard to location, so that only the applied patches need tobe severed and that the cutting element does not partially also need tosever the composite foil of the packaging.

Although one has then alternatively incorporated notches into suchcomposite foils, wherein these notches only went down to the barrierlayer, so that the cutting element only needed to sever this barrierlayer and the plastic foil lying therebelow, however, clearly thissolution once again demands a significantly greater precision of theassembly of the plastic closure onto the packaging.

A further variant is known from PCT Publication WO 2004/000667. Here,the advance of the cutting element in a first step is effected in apurely translatory manner by way of a drive, as is already known fromthe mentioned European Patent Reference EP0328652, and on reaching itsdeepest position, the cutting element from then on only rotates.

Whereas initially and particularly in the context of so-called cardboardcomposite packaging, one operated with a multitude of perforating teeth,later one has predominantly departed from this approach. One main reasonfor this multitude of perforating teeth is to be seen in the fact thatthe cardboard layer of such packaging requires a relatively high force,in order to be pierced. The multitude of teeth then indeed no longereffects a cutting, but more of a sawing.

The structure of such cardboard composite foils however has been changedover the years. One the one hand the cardboard layer has becomeincreasingly thinner, and on the other hand several different layers ofplastics have been applied, which in principle have again and againplaced different demands upon the cutting element. Accordingly, amultitude of patent applications concern themselves with the shape andthe arrangement of the perforating teeth and cutting teeth. Typicalexamples of such designs for example are to be deduced from PCTPublication WO 2004/083055 or European Patent Reference EP 1533240. Aneven more complex arrangement is shown for example in European PatentReference EP 1795456. A reason for the many embodiments, as alreadymentioned, are the different types packaging foils, wherein inparticular bag pouches (tubular bags) which have recently becomewidespread on the market and which are purely of plastic composite foilsare a reason. Whereas the perforation is effected relatively reliablywith only one or few perforating teeth in many cases, the subsequentcutting activity however is much more of a problem. These two differentactivities specifically, during the perforation, necessitate arelatively high force with a simultaneously low relative movement,whereas subsequently with the cutting procedure, a significantly reducedforce with as large as possible a relative movement of the cutting edgerelative to the foil to be severed is necessary. Here, no difference ismade with the plastic closures which are obtainable on the market.

Also, it has been found that with self-opening plastic closures with arotating cutting element, the foil to be cut, on account of its highelasticity as is practically the case of all polyethylene, leads to thematerial being drawn out and simultaneously accumulating on the cuttingedge in the rotation direction and thus practically rendering thecutting edge ineffective. This then either leads to an incomplete lineof cut or to an uncontrolled tearing of the packaging foil. This onlypartly opened container then only allows for a poor emptying.

It is thus one object of this invention to provide a self-openingplastic closure of the initially mentioned type, which can be actuatedwith a different force in dependence on the advance path, in order tomaster the problems which have been discussed.

SUMMARY OF THE INVENTION

The above object and others are achieved by a self-opening plasticclosure as described in this specification and in the claims, whereinenvisaged means include a first and a second advance mechanism whichengage one after the other and which effect different axial advancepaths per revolution.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantageous embodiments of the subject matter of this inventionare discussed and deduced in view of the following description and thedrawings, wherein:

FIG. 1 shows a perspective view of an assembled, self-opening plasticclosure, in a view from above;

FIG. 2 shows a view onto a lower side of the plastic closure of FIG. 1;

FIG. 3 shows a screw cap of the self-opening plastic closure, in anaxial vertical section;

FIG. 4 shows a perspective view onto the lower side;

FIG. 5 shows an axial vertical section taken through the pour-out spout;

FIG. 6 shows a perspective view of the pour-out spout of FIG. 5;

FIG. 7 shows the cutting element in a perspective view;

FIGS. 8 and 9 show cutting elements and the pour-out spout manufacturedas one piece, together before applying the screw cap, in two differentperspective views; and

FIGS. 10-13 show the assembled, self-opening plastic closure, in eachcase in a diametrical section, at different stages of opening.

DETAILED DESCRIPTION OF THE INVENTION

One possible design of the self-opening plastic closure according to theinvention and which in its entirety is indicated at element referencenumeral 1 is perspectively shown in FIG. 1. In this view, one canpractically only recognize the screw cap 2 and that part of the pour-outspout 3 which is not covered by the screw cap. This non-covered part ofthe pour-out spout 3 is practically only the peripheral flange 31 at theend. From the outside, on the screw cap 2, one can recognize itsperipheral lateral wall 20, on whose lower end a guarantee strip 22 isintegrally formed via suitable predetermined breakage bridges which arenot visible here. The peripheral lateral wall 20 carries the upper coversurface 21. A multitude of gripping ribs 29 which increase the grippingability for the user on handling the screw cap are incorporated at theoutside on the lateral wall 20.

The same, self-opening plastic closure 1 is represented obliquely frombelow in the assembled condition in FIG. 2. In the position shown here,the self-opening plastic closure 1 is represented in an intermediateposition, with which the cutting element 4 with the perforating teetharranged thereon is represented already projecting slightly out of thepour-out spout 2, and the cutting element 4 is therefore at least partlyvisible. The pour-out spout 3 from now on is partly visible from thelower side, so that one now recognizes an energy directing rib 32 onthis lower side. The design of the energy directing rib is representedhere as a single, peripheral rib, but other design forms or shapes ofsuch energy directing ribs 32 are known, and their design is accordinglyadapted to the weld connection which is to be formed, and to thematerial pairing.

The three parts which form the self-opening plastic closure arehereinafter described individually and their interaction explainedafterwards. The screw cap 2 in the FIGS. 3 and 4 is represented on itsown. As every screw cap, this includes the already mentioned lateralwall (skirt) 20 and the cover surface 21 terminating the screw cap. Thelikewise already mentioned guarantee strip 22 is integrally formed herevia predetermined breakage bridges not specially shown here, below thelateral wall in an aligned manner. Here, one can recognize the innerthread 23 on the lateral wall 20, in particular in the sectioned viewaccording to FIG. 3. This inner thread 23 serves for interacting with anouter thread on the pour-out spout 3. A first annular wall 24 can berecognized in this sectioned drawing and this in this sectioned drawinghas a different height. The first annular wall 24 in this figure at theright side of the middle axis is higher than on the left of the middleaxis. The first annular wall 24 in this embodiment is completelyperipheral and runs from a lowest point to the highest point, whereinthe lowest point represents the starting point on opening for the firsttime, and the highest point corresponds to an end point after a rotationof 360°, wherein this represents the end point of the advance path of afirst advance mechanism.

The ramp-like first annular wall 24 has a sliding surface 25 whichpoints away from the cover surface 21. This sliding surface 25 thencooperates with a second sliding surface of a first advance mechanism,wherein this will be dealt with later. A second annular wall 26 isintegrally formed on the lower side of the cover surface 21,concentrically to the first annular wall 24, offset inwards. This secondannular wall 26 has the same height over its entire periphery. The axiallength of the second annular wall 26 here is larger than the axiallength of the lateral wall 20. This is thus coherent so that the screwcap 2 in the assembled condition is held with its guarantee strip 22 viathe flange 31 of the pour-out spout and distanced to this. An outerthread 27 is integrally formed on the outer side of this second annularwall 26. This outer thread 27 forms part of a second advance mechanism.

In principle, four concentric annular walls are integrally formed belowthe cover surface 21, wherein the outer annular wall represents thelateral wall 20 and the innermost annular wall forms the so-calledsecond annular wall 26. Between the second annular wall 26 and thelateral wall 20, from the inside to the outside follows firstly thefirst annular wall 24 and thereafter an annular wall forming a so-calledsealing olive 28 which in the closed condition of the closure afteropening for the first time comes to bear on the inner side of thepour-out spout in a sealing manner. The packaging foil is still closedin the assembled condition before opening for the first time, and thesealing function of the sealing olive 28 is not yet necessary.

The pour-out spout 3 is shown on its own in each of the FIGS. 5 and 6,wherein FIG. 5 shows a diametrical section and FIG. 6 a perspectiveview, viewed from above into the pour-out spout. The pour-out spout 3includes a cylindrical pour-out 30 of the one lower, edge-sideperipheral flange 31. This flange 31 comprises the mentioned energydirecting rib 32 on its lower side serving for being attached onto apackaging receptacle for this. Basically, the flange can be bonded onsuch a packaging, wherein this is particularly the case with so-calledbrik packaging, which include multi-layered packaging foils whichcomprise a cardboard layer, single-layer or multi-layer plastic and atleast one barrier layer. The pour-out spout, and thus the complete,self-opening plastic closure can also be welded on such a packagingfoil, in particular if the outermost layer of the packaging foil is aplastic layer. Thus, here it is mostly only a welding and hardly abonding which is considered if the self-opening plastic closure 1 isattached onto a bag pouch which mostly consists of a complex,multi-layered plastic foil with a barrier layer. An axially runningguide rib 34 can be recognized on the inner side of the cylindricalpour-out 30. This axial guide rib runs from approximately the upper edgeof the cylindrical pour-out 30 to the lower edge of the pour-out 30.This axial guide rib 34 serves for the secure axial guiding of thecutting element 4 which is yet to be described, within the cylindricalpour-out 30 of the pour-out spout 3. Moreover, several detent lobes 35are arranged on the inner wall of the cylindrical pour-out 30 in thelower region relative close to the plane which defines the peripheralflange 31. Actually, this is practically two detent lobes 35 which arearranged directly above one another. These serve for holding the cuttingelement in a defined lowermost position. Moreover, several separatedpredetermined breakage bridge parts 36 can be likewise recognized on theinner wall of the cylindrical pour-out 30 in the upper quarter which isdiscussed in more detail later. The abutment ribs 37 which are attachedon the outer side of the cylindrical pour-out 30 and which extend downto the peripheral flange 32 serve for interacting with the guaranteestrip. Finally, in FIG. 6 one yet recognizes a notch which is recessedon the outer periphery of the flange 31 and which forms an orientationnotch 38 which merely serves for the orientation of the different partsin an assembly plant.

The cutting element is shown on its own in a perspective view in FIG. 7and it comprises a cylinder wall 40 whose upper edge is designed as aramp-like face wall 41. This ramp-like face wall with regard to lengthand gradient is designed the same as the ramp-like annular wall 24 ofthe screw cap 2. The ramp-like face wall 41 comprises a sliding surface42 which in the assembled condition of the self-opening plastic closures1 lies on the sliding surface 25 of the first ramp-like annular wall 24.Here, several perforating teeth 43 are integrally formed on this edge inthe axial direction of the sliding surface 42. Each perforating tooth 43is delimited by perforating edges 44 and together they enclose an acuteangle. Cutting edges 45 are subsequent to these perforation edges 44, atboth sides. Two cutting edges 45 which are directed to the sameperforating tooth 43 in each case together enclose an obtuse angle. Theperforating teeth 43 with the acute angle which the perforating edges 44enclose, only execute a small cutting function, but practically carryout only a piecing function, in the case of an axial movement. Thesubsequent cutting edges 45 which run in a relatively shallow manner,with the continued, purely translatory advance of the cutting elementwhich is effected in the axial direction and in the direction of thepackaging foil now execute a significantly greater relative movement,with regard to the peripheral line per advance path section. The cuttingmovement is thus effected immediately after the perforation of thepackaging foil with the second advance mechanism. Trials have shown thatfrom now on, the cutting movement immediately continues the incisionswhich arise on perforation and are in the running direction of theperforating edges, into a cutting line.

Reinforcement ribs 491 which extend from a peripheral collar 47 to asclosely as possible to the tip of the respective perforating tooth 43are integrally formed on the outer side of the cylinder wall 40 of thecutting element 4. The peripheral collar 47 runs in a planeperpendicular to the middle axis of the cutting element. The upper edgeof the peripheral collar 47 is arranged at the height of the lowermostpoint of the ramp-like face wall or sliding surface 42. The peripheralcollar 47 comprises a guide recess 49, at least at those locations, atwhich the axial guide rib 34 is arranged in the pour-out spout. Also,several separated predetermined breakage bridges 48 which before theassembly connect the cutting element 4 to the pour-out spout 3, are tobe recognized on the outer side of the peripheral collar 47. Theseseparated predetermined breakage bridges 48 are connected to theseparated predetermined breakage bridges 36 before assembly.

The cutting element 4 and the pour-out spout 3 together form asingle-piece construction unit 70 which in the FIGS. 8 and 9 is shown ina perspective view with different viewing angles in each case.

The mentioned orientation notch 38 in the flange 31 of the pour-out part3 is finally of significance, since the pour-out part 3 and the cuttingelement 4 are preferably manufactured as a single-part unit 70. Theeffort on production and assembly is thus reduced. The single-part unit70 is realized such that the cutting element 4 lies completely withinthe pour-out 30 of the pour-out spout 3. In this position, the highestpoint of the ramp-like face wall 41 of the cutting element 4 at leastapproximately lies in the plane which is spanned by the upper edge 39 ofthe cylindrical pour-out 30.

Now, on assembly, the screw cap 2 is placed onto the single-part unit70, wherein the screw cap is aligned so that the highest point 493 ofthe ramp-like face wall 41 comes to bear on that point which correspondsto the point which lies closest to the cover surface 21 on the firstramp-like annular wall 24 of the screw cap 2. On axially pushingtogether, preferably the predetermined breakage bridges between theperipheral collar 47 and the inner wall of the pour-out 30 are separatedpreferably at the last moment of the pushing-together, so that only theseparated predetermined breakage bridges 36 and 48 continue to bepresent.

The cutting element 4 is simultaneously moved slightly axiallydownwards, so that the point of the cutting element 4 which is lowermostin the axial direction, specifically the tips of the perforating teeth43 is still above the plane which defines the lower side of the flange31. It is thus ensured that the plastic closure 1 does not lie on thepackaging foil of the receptacle, on which it is to be fastened, alreadywhen welding on the assembled, self-opening plastic closure 1. Thisposition is now represented in FIG. 10 in a diametrical section. Thisposition shows the self-opening plastic closure 1 according to thisinvention, in the assembled position before opening for the first time.The predetermined breakage locations between the screw cap 2 and theguarantee strip 22 which is integrally formed thereon are still intact,but since the diametrical section does not run through a predeterminedbreakage bridge, this cannot be recognized in the figure. The firstadvance mechanism 50 is in its starting position in this position. Thisfirst advance mechanism 50, as mentioned, includes the first ramp-likeannular wall 24 with its sliding surface 25, wherein its sliding surface25 lies on the sliding surface 42 of the annular face wall 41 of thecutting element 40 over the entire periphery.

The screw cap 2 is now represented rotated by 360° in FIG. 11. On theleft side one now recognizes the ramp-like face wall 41 which ispractically at the highest point, whereas the highest location of theramp-like annular wall 24 has just been exceeded and therefore is nowonly represented in a dotted manner. The opposite position on the rightside shows the ramp-like annular wall 24 which here is only half ashigh, since the sliding surface 42 on this side has already moved byjust as much downwards.

The second advance mechanism 60 now assumes its function in thisposition, in which the first advance mechanism has now reached itsmaximum advance path. As is evident on the right as well as left of themiddle axis, this second advance mechanism 60, including the outerthread 27 on the second annular wall 26 is meshed with the inner thread492 on the cylinder wall 40 of the cutting element 4. In this position,the first advance mechanism 50 as described in FIG. 10 has now moved thecutting element 4 already so far downwards in the direction of theflange, that the perforating teeth 43 lie below the plane which isspanned by the flange. The perforating teeth 43 have already perforatedthe closure foil in the case that the self-opening plastic closure iswelded on a packaging foil.

If the screw cap 2 is moved by a further complete revolution, then thecutting element 4 is once again moved further in the direction of theflange 31 and not only the perforating tooth with its perforating edges44, but also the adjacent cutting edges 45 just as the fold-over edge 46now lie below the plane spanned by the peripheral flange, and thepackaging on which the self-opening plastic closure 1 is attached, isnow completely cut open and only continues to be connected to thepackaging in the region of or near the fold-over edge 46. The cut-openpackaging foil is folded over to outside the region of the pour-out 30.In the shown position, the inner thread 23 is connected to the outerthread 33 of the pour-out spout, as also the outer thread 27 on thesecond annular wall 26 is still meshed with the inner thread 492 of thecutting element 4.

If one now screws the screw cap 2 again by half a revolution, then theposition shown in FIG. 13 is reached. The inner thread 492 is no longermeshed with the outer thread 27 on the second annular wall 26. However,on the left side in this figure, one simultaneously recognizes that theperipheral collar 47 on the cutting element 4 is snapped in with thedetent lobes 35 on the inner side of the pour-out 30. With this, thecutting element 4 now remains in this position, even if the screw cap 2is still completely screwed off from the pour-out spout 3. After one hasremoved a share of the contents out of the packaging and screwed thescrew cap 2 back on, then with each opening and closing procedure, it isnow only the screw cap 2 which moves, while the cutting element 4remains in the unchanged position.

As previously mentioned, only a preferred embodiment is shown in thedrawing. Further embodiments which are not described here are alsopossible without departing from the inventive concept. Thus of courseall 3 components of the self-opening plastic closure 1, specifically thescrew cap 2, the pour-out spout 3 and the cutting element 4 can all bemanufactured separately. Here too, the described sequence of the firstand second advance mechanism 50, 60 can of course be changed. In otherwords, the first annular wall can be designed as a normal cylindricalannular wall and be provided with suitable threads, whereas the secondannular wall is then designed as a ramp-like annular wall. This secondannular wall would then need to interact with the ramp-like face wall ofthe cutting element. Although this solution is of course alsoconceivable, the representation of this solution however has beenomitted, and this variant is less preferred compared to the representedembodiment, because such a variant reduces the diameter of the cuttingelement and accordingly, in order to obtain the same opening, the wholeself-opening plastic closure would need to be designed larger, whichhere would entail an increased material consumption.

Apart from the explicitly described solution and the variants mentionedabove, it is possible to realize the first as well as the second advancemechanism both with a thread or both with advance ramps. These withregard to height merely need to be arranged so that both advancemechanisms cannot be engaged simultaneously.

Also, the first advance mechanism 50, instead of extending over 360° asshown, can be also designed from two ramp-like sections extending over180° . This leads to a symmetrical force transmission, wherein the ratioof the advance path per revolution increases, just as the necessaryforce effort on opening for the first time.

Instead of the variant with three perforating teeth which is shown here,also only one or two perforating teeth or more than three perforatingteeth can be present. This is made dependent on the diameter of theself-opening plastic closure 1. If one provides only one perforatingtooth 43, then the adjacent cutting edges 45 extend in a gapless mannerabout at least two thirds of the periphery. The fold-over edge 46 thenlies diametrically opposite the perforating tooth 43.

1. A self-opening plastic closure (1) including a pour-out spout (3)with a flange (31) for connection to a single-layer or a multi-layerpackaging foil of a closed packaging, with a cylindrical cutting element(4) movably guided within the pour-out spout (3), and with a screw cap(2) with a lateral wall (20) with an inner thread (23) and with a coversurface (21), the screw cap (2) screw-connected to the pour-out spout(3) with an outer thread (33), and the screw cap (2) and the cuttingelement (4) converting a screw movement of the screw cap (2) into apurely translatory relative movement of the cutting element (4) to thepour-out spout (3), the converting comprising a first advance mechanism(50) and a second advance mechanism (60) engaging one after the otherand effecting different axial advance paths per revolution.
 2. Aself-opening plastic closure according to claim 1, wherein the firstadvance mechanism (50) includes a first ramp-like annular wall (24)integrally formed on an inner side of the cover surface (21) of thescrew cap (2), and a mutually opposite face wall (41) running in aramp-like manner on the cylindrical cutting element (4).
 3. Aself-opening plastic closure according to claim 1, wherein the secondadvance mechanism (60) includes an inner thread (492) on the cylindricalcutting element (4) and of an outer thread (27) on a second angular wall(26) arranged on an inner side of the cover surface (21) in the screwcap (2).
 4. A self-opening plastic closure according to claim 3, whereinthe second annular wall (26) is arranged concentrically within the firstannular wall (24).
 5. A self-opening plastic closure according to claim1, wherein a gradient of the first advance mechanism (50) is less than agradient of the second advance mechanism (60).
 6. A self-opening plasticclosure according to claim 2, wherein the cutting element (4) on an endwhich lies opposite the ramp-like face wall (41) has at least oneperforating tooth (43) to which a cutting edge (45) connects in aperipheral direction at both sides, and a fold-over edge (46) is presentoutside a region of the cutting edges and of the at least oneperforating tooth (43).
 7. A self-opening plastic closure according toclaim 6, wherein only one perforating tooth (43) with connecting cuttingedges (45) is present, and the cutting edges (45) extend in a gaplessmanner about at least two thirds of a periphery and the fold-over edge(46) is arranged diametrically opposite the perforating tooth (43).
 8. Aself-opening plastic closure according to claim 6, wherein at least twoperforating teeth (43) present and the cutting edges extend in a gaplessmanner on at least two thirds of the periphery, and the fold-over edge(46) is arranged in a remaining cutting-edge free region.
 9. Aself-opening plastic closure according to claim 6, wherein the cuttingedges (46), which are adjacent the same perforating tooth (43) enclosean obtuse angle.
 10. A self-opening plastic closure according to claim6, wherein an axial advance path of the first advance mechanism (50) iscapable of advancing the cutting element (4) so far until a transitionof the at least one cutting tooth (43) to the adjacent cutting edges(46) at least approximately lies in a plane of the flange (31) of thepour-out spout (3).
 11. A self-opening plastic closure according toclaim 10, wherein the advance path of the second advance mechanism (60)is capable of advancing the cutting element (4) so far until thefold-over edge (46) at least approximately lies in the plane of theflange (31) of the pour-out spout (3).
 12. A self-opening plasticclosure according to claim 1, wherein the purely translatoiy movement ofthe cutting element (4) relative to the pour-out spout (3) is realizedby at least one axially running guide rib (34) on the inner side of acylindrical pour-out (30) of the pour-out spout (3), and a guide recess(49) is realized in a peripheral collar (47) which is arranged at theoutside on the cutting element (4).
 13. A self-opening plastic closureaccording to claim 12, wherein detent lobes (35) are present on theinner surface of the pour-out (30) at a height close to the flange (31),into which lobes in a lowermost advance position of the cutting element(4) its peripheral collar snaps in wherein the position is equal to theend of the advance path of the second advance mechanism (60).
 14. Aself-opening plastic closure according to claim 1, wherein the pour-outspout (3) and the cutting element (4) are manufactured in a separablemanner as a single piece, as one component (70).
 15. A self-openingplastic closure according to claim 2, wherein the second annular wall(26) is arranged concentrically within the first annular wall (24).